We hypothesise that intravenously-delivered autologous bone marrow cellular therapy (BMCT) in chronic MS offers significant benefit. We hypothesize also that the mechanisms are multiple, and include immunomodulation and reparative and/or neuroprotective effects within the CNS; and are offered by one or more BM stem cell sub-populations, jointly contributing to the therapeutic impact. Exploring and understanding these mechanisms, and the biology of the cells responsible, will allow the development of more effective reparative cell therapy in MS.